Evaluation of solid state properties of solid dispersions prepared by hot-melt extrusion and solvent co-precipitation.

The solid state properties of solid dispersions of Compound A in hypromellose acetate succinate (HPMC-AS) prepared by hot-melt extrusion (HME) and solvent co-precipitation (CP) processes were evaluated using powder X-ray diffractometry (PXRD), thermal analysis, optical microscopy, scanning electron microscopy (SEM), FT-IR and Raman spectroscopy, water vapor sorption analyzer, and surface area by BET. PXRD indicated that both processes converted the crystalline drug into amorphous solid dispersions with a glass transition temperature around 104-107 degrees C and both products have similar spectroscopic and hygroscopic properties. The two products have similar true densities; however, the CP product is more porous and has a larger specific surface area than the HME product, as indicated by the BET results and SEM micrographs. Dissolution study using USP apparatus 2 showed that the CP product had a faster dissolution profile, but slower intrinsic dissolution rate than the HME product. The two products have acceptable physical stability after storage in 40 degrees C/75% RH chamber for 3 months. However, the HME product is more stable than the CP product in aqueous suspension formulation.

Determination of drug-polymer binding constants by affinity capillary electrophoresis for aryl propionic acid derivatives and related compounds.

The binding constants (K(b)s) of 17 aryl propionic acid derivatives (APADs) and related compounds with polyvinylpyrrolidone (PVP K30) and vinylpyrrolidone-vinyl acetate copolymer (Kollidon VA64) in aqueous media were determined by affinity capillary electrophoreses (ACE). The K(b)s of APAD to polymers increase with octanol-water partition coefficients of the compounds. Kollidon VA64 is a stronger binder than PVP K30 to APAD compounds. The K(b)s are greater at pH 4 than at pH 9. Both hydrophobic interaction and hydrogen bonding may be involved. However, hydrophobic interaction appears to be dominant. The ACE method is simple and fast, which could be used to study drug-polymer interaction in aqueous media.

Highly efficient miniaturized coprecipitation screening (MiCoS) for amorphous solid dispersion formulation development.

Microprecipitated bulk powder (MBP) is a novel solid dispersion technology to manufacture amorphous formulations of poorly soluble compounds that cannot be processed by spray drying or melt extrusion. An efficient high-throughput screening method has been developed to aid the selection of polymer type, drug loading and antisolvent to solvent ratio for MBP formulation development. With a 96-well platform, the miniaturized coprecipitation screening (MiCoS) includes mixing of drug and polymer in dimethylacetamide, controlled precipitation to generate MBP, filtration/washing, drying and high throughput characterization. The integrated MiCoS approach has been demonstrated with a model compound, glybenclamide. Based on the solid state stability and kinetic solubility of the MBP, hydroxypropylmethylcellulose acetate succinate polymer with 40% or lower drug loading, and antisolvent (0.01 N HCl) to solvent (dimethylacetamide) ratio of 5:1 or higher were selected to make glybenclamide MBP. MiCoS can be applied to both early and late stage formulation processing. In early stage research programs, the system can be used to enable efficacy, pharmacokinetics or mini-toxicology studies for poorly water soluble molecules using minimal amount of drug substance (2-10mg). In late stage development programs, MiCoS can be used to optimize MBP formulation by expanding the experimental design space to include additional formulation variants.

Improved human bioavailability of vemurafenib, a practically insoluble drug, using an amorphous polymer-stabilized solid dispersion prepared by a solvent-controlled coprecipitation process.

The present work deals with improving the solubility of vemurafenib, a practically insoluble drug, by converting it into an amorphous-solid dispersion using a solvent-controlled precipitation process. The dispersion containing vemurafenib and hypromellose acetate succinate (HPMCAS), an enteric polymer, is termed microprecipitated bulk powder (MBP), in which the drug is uniformly dispersed within the polymeric substrate. HPMCAS was found to be the most suitable polymer for vemurafenib MBP, among a series of enteric polymers based on superior physical stability and drug-release characteristics of the MBP. The MBP provided a greater rate and extent of dissolution than crystalline drug, reaching an apparent drug concentration of 28-35 µg/mL, almost 30-fold higher than solubility of crystalline drug at 1 µg/mL. The supersaturation was also maintained for more than 4 h. Upon exposure to high temperature and humidity, the MBP was destabilized, resulting in crystallization and lower dissolution rate. The control of moisture and temperature is essential to maintain the stability of the MBP. In a relative human bioavailability study, vemurafenib MBP provided a four- to fivefold increase in exposure compared with crystalline drug. Improving solubility with an amorphous-solid dispersion is a viable strategy for the development of practically insoluble compounds.

Development of novel microprecipitated bulk powder (MBP) technology for manufacturing stable amorphous formulations of poorly soluble drugs.

A novel method was developed to manufacture amorphous formulations of poorly soluble compounds that cannot be processed with existing methods such as spray drying and melt extrusion. The manufacturing process and the characterization of the resulting amorphous dispersion are presented via examples of two research compounds. The novel process is utilized N,N-dimethylacetamide (DMA) to dissolve the drug and the selected ionic polymer. This solution is then co-precipitated into aqueous medium. The solvent is extracted out by washing and the co-precipitated material is isolated by filtration followed by drying. The dried material is referred to as microprecipitated bulk powder (MBP). The amorphous form prepared using this method not only provides excellent in vitro and in vivo performance but also showed excellent stability. The stabilization of amorphous dispersion is attributed to the high T(g), ionic nature of the polymer that help to stabilize the amorphous form by possible ionic interactions, and/or due to the insolubility of polymer in water. In addition to being an alternate technology for amorphous formulation of difficult compounds, MBP technology provides advantages with respect to stability, density and downstream processing.

Affinity purification and characterization of an anti-PEG IgM.

Anti-PEG IgM was purified by affinity chromatography using variable length PEG chains (5, 10, 20 and 30 kDa) as affinity ligands. Maximal binding of anti-PEG IgM was observed using the 30 kDa PEG-derivatized NuGel (single passage). Purified anti-PEG IgM was characterized for binding to PEG functionalized proteins/peptides by surface plasmon resonance, western blotting and ELISA. Anti-PEG IgM, in solution and adsorbed on 20 kDa PEG-derivatized NuGel, was subjected to pepsin digestion followed by affinity chromatography. SDS-PAGE analysis of eluates in both preparations yielded one fragment that was similar in size. However, an additional lower molecular weight band was observed in solution-digested affinity purified material that was not present in the eluate from the material subjected to pepsin digestion on the affinity matrix. The lower MW fragment could be eluted under milder conditions, suggesting loss of binding multiplicity. Analysis by mass spectrometry yielded molecular weights of 132 kDa (both) and 82 kDa (solution) for the respective fragments. N-terminal sequencing of both fragments resulted in primary sequences (heavy and light chains) that were not only identical to each other but also to those of native IgM. The anti-PEG IgM fragments were characterized for binding to pegylated interferon alfa-2a by ELISA. The results from these studies suggest that affinity purified anti-PEG IgM and fragments can be used as probes in detection assays for PEG functionalized biotherapeutics in pre-clinical and clinical studies.

Size exclusion chromatography with Corona charged aerosol detector for the analysis of polyethylene glycol polymer.

A technique of using size exclusion chromatography (SEC) with the Corona charged aerosol detector (CAD) was developed and evaluated in comparison with refractive index (RI) and evaporative light scattering detection (ELSD) for fast screening of polyethylene glycol (PEG), a polymer used in preparing pegylated pharmaceutical compounds. These detection techniques were used in the analysis of multiple lots of PEG reagents. CAD was found to provide more accurate impurity and polydispersity profiles of PEG reagents that better differentiate their quality, while RI was not suitable for this application due to its low sensitivity and ELSD led to underestimation of the impurity and polydispersity. The accuracy of polydispersity determination by SEC-CAD was validated against a commercial reference standard of known polydispersity. The SEC-CAD technique and the observed differences between the three detectors can also be applied to polymer analysis in general.